Three-dimensional image observation microscope system

ABSTRACT

A three-dimensional image observation microscope system includes an imaging unit that captures images focused at different object point distances in an optical axis direction and a display unit that displays a plurality of the images captured by the imaging unit for overlaid observation along the line of sight of a viewer as a three-dimensional image. The imaging unit includes an objective optical system that obtains an image of an object, a zoom optical system that controls the magnification of the image obtained by the objective optical system, and a plurality of image pickup devices that capture the images with a magnification controlled by the zoom optical system. Specified conditions related to focal length, numerical apertures, inclinations, magnifications and distances within the imaging unit and the display unit are satisfied.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of foreign priority of JP2005-16189, filed Jan. 24, 2005, the contents of which are herebyincorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a three-dimensional image observationmicroscope system suitable for observing objects to be worked on.Specifically, the present invention relates to a microscope system thatincludes an imaging unit and a display unit for three-dimensionalobservation using electronic images.

BACKGROUND OF THE INVENTION

Stereomicroscopes are conventionally used in fine processing under amicroscope, or surgical operations under a microscope where, forexample, accurate work on a small area around a lesion is required.Recently, there has been demand for conducting these tasks using remotecontrol. If the capabilities of a remote operation are available, aprocessing engineer or a doctor can conduct the task from a remotelocation without traveling to the actual processing or operating site.It is desirable for realizing such a remote operation that images of anobject observed by a stereomicroscope be formed and displayed on adisplay unit.

An apparatus that allows the viewer to three-dimensionally observedisplayed images with the help of binocular parallax is known. Forexample, in some stereoscopic image observation apparatuses, images ofan object are captured from different angles so that the effects ofbinocular parallax appear in images displayed on a display unit, and theviewer observes separate left and right images having parallax with hisleft and right eyes, respectively, for three-dimensional observation.

In such an apparatus, the resolution on the image pickup surfacedeteriorates as the optical system of the imaging part has a largerdepth of field. On the other hand, as the optical system of the imagingpart has a larger aperture for higher resolution on the image pickupsurface, the depth of field inherently becomes smaller, and this cancreate problems. In applying a stereoscopic image observation apparatusto surgical operations and fine processing under a microscope,deterioration in resolution of observed images is not acceptable becauseit directly affects the accuracy of the operation performed by theoperator. When such a stereoscopic image observation apparatus is usedin a surgical operation under a microscope, the optical system of theimaging part inherently provides a smaller depth of field in order toobtain higher resolution observation images. Consequently, the operatoris required to frequently refocus during the operation, causing loweredperformance and operator fatigue.

It is known that stereoscopic images provided by the prior artstereoscopic image observation apparatuses are difficult to seethree-dimensionally in the line of sight of the viewer. In other words,the larger features of an object image, for example, the general contourof an object, are relatively easy to see three-dimensionally. However,an object near the direction of the line of sight of the viewer isobserved as lying in a plane with no three-dimensional appearance.Therefore, the viewer cannot recognize the object as beingthree-dimensional. Images lacking a three-dimensional appearance in theline of sight of the viewer may cause the operator to misunderstand theshape of the object and, therefore, are not suitable for theapplications described above.

In order to solve the above problem, techniques using lenticular opticalelements and holograms that can provide three-dimensional information inthe line of sight of the viewer have been proposed in the prior art.However, these techniques do not provide an imaging system withsufficient resolution and it is difficult to put such techniques intopractical use. Techniques using DFD (depth-fused 3D) devices have beenproposed in Japanese Laid-Open Patent Application Nos. 2000-214413 and2000-341473.

Japanese Laid-Open Patent Application No. 2000-214413 discloses thatpositional relationships among multiple images may be expressed bychanging display densities of the same point of multiple images arrangedin the line of sight. Japanese Laid-Open Patent Application No.2000-341473 discloses a case in which a focused image and an unfocusedimage that are spaced from each other in the optical axis direction areseparately captured and then displayed in an overlaid manner in order toincrease the amount of information in the line of sight of an observerso that the observer recognizes a three-dimensional image.

It is generally considered in the prior art that an observer simplyrecognizes multiple images and never identifies a three-dimensionalimage when images are overlaid. Further, an unfocused image isconsidered to cause deterioration of an image, such as by reducing thecontrast. Therefore, image correction such as deletion of unfocusedareas is made.

However, in fact, when an unfocused image is overlaid in the line ofsight of a viewer without changing the unfocused image, the unfocusedimage contributes to giving a three-dimensional appearance in the lineof sight of the viewer, and thus the viewer can observe a naturalthree-dimensional image. The techniques described in Japanese Laid-OpenPatent Application Nos. 2000-214413 and 2000-341473, described above,utilize the fact that the viewer recognizes multiple images in the lineof sight as point information and considers changes in image contrast(i.e., changes in density of an image) to be three-dimensionalinformation. However, three-dimensional images created by thosetechniques do not have a sufficient three-dimensional appearance forusing them in surgical operations under a microscope.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a three-dimensional image observationmicroscope system wherein an observed object is displayed as athree-dimensional image that includes sufficient three-dimensionalinformation for surgical operations under a microscope, that favorablyreproduces the three-dimensional appearance of the observed object, andthat does not cause fatigue of the viewer after a prolonged observation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given below and the accompanying drawings, whichare given by way of illustration only and thus are not limitative of thepresent invention, wherein:

FIG. 1 shows an imaging unit of a three-dimensional image observationmicroscope system of Embodiment 1;

FIG. 2 shows a display unit of the three-dimensional image observationmicroscope system of Embodiment 1;

FIG. 3 shows an imaging unit of a three-dimensional image observationmicroscope system of Embodiment 2;

FIG. 4 shows a display unit of the three-dimensional image observationmicroscope system of Embodiment 2;

FIG. 5 shows an imaging unit of a three-dimensional image observationmicroscope system of Embodiment 3;

FIG. 6 shows a display unit of the three-dimensional image observationmicroscope system of Embodiment 3;

FIG. 7 shows an imaging unit of a three-dimensional image observationmicroscope system of Embodiment 4;

FIG. 8 shows the apertures 35L and 35R of left and right aperturediaphragms overlapped with the aperture 34 of an imaging unit;

FIG. 9 shows a display unit of the three-dimensional image observationmicroscope system of Embodiment 4;

FIG. 10 shows the relationships among parameters of the left eye displayunit 1;

FIG. 11 shows the configuration of the three-dimensional imageobservation microscope system of Embodiment 5;

FIG. 12 is an enlarged view of the image pickup surface 52 of the imagepickup device 53, and its surrounding area, of Embodiment 5;

FIG. 13 is an enlarged view of the display surface of a display Mn, andits surrounding area, of Embodiment 5;

FIG. 14 shows a pair of black and white lines that form part of a testchart: and

FIG. 15 shows a test chart that includes a pair of black and white linesas shown in FIG. 14 positioned at a location in front of the objectiveoptical system that is conjugate with an image pickup surface of animage pickup device.

DETAILED DESCRIPTION

The three-dimensional image observation microscope system of the presentinvention includes an imaging unit that captures images focused atdifferent object point distances in an optical axis direction and adisplay unit that displays a plurality of images that are captured bythe imaging unit for overlaid observation along the line of sight of aviewer.

The imaging unit includes an objective optical system that obtains animage of an object, a zoom optical system that controls themagnification of the image obtained by the objective optical system, anda plurality of image pickup devices that capture these images with amagnification that is controlled by the zoom optical system. The opticalsystem of the imaging unit includes the objective optical system, thezoom optical system, and any other optics that the imaging unit uses toform an image.

Additionally, it is desirable that the zoom optical system be placed inan afocal light beam. Also, it is desirable that the followingConditions (1), (2), and (3) be satisfied:fob·NAmax≧15 mm  Condition (1)NAmin≧0.02  Condition (2)0.25≦d·NA/(R·β)≦2  Condition (3)where

-   -   fob is the focal length, in mm, of the objective optical system;    -   NAmax is the maximum object-side numerical aperture of the        objective optical system of the imaging unit;    -   NAmin is the minimum object-side numerical aperture of the        objective optical system of the imaging unit;    -   d is the distance, in mm, between two adjacent image pickup        surfaces of the image pickup devices;    -   NA is the object-side numerical aperture of the objective        optical system of the imaging unit when the zoom optical system        has a magnification β;    -   R is the width, in mm, of a pair of black and white lines when        the pair of black and white lines are part of a test chart        having evenly-spaced, parallel sets of black and white lines and        the test chart is placed in a plane that is conjugate with an        image pickup surface of one of the image pickup devices with        respect to the objective optical system of the imaging unit so        that an image of the pair of black and white lines is captured        on the image pickup surface of one of the image pickup devices        in such a maimer that the black and white lines are displayed on        a monitor with a contrast of 10% through a circuit system that        processes image signals sent from the image pickup devices;    -   βis the magnification of the zoom optical system.

Condition (1) ensures that proper work can be done using thethree-dimensional image observation microscope system. If Condition (1)is not satisfied, a sufficient distance is not preserved for an objectbeing imaged and the imaging device. Therefore, an engineer attemptingfine processing or an operator in a surgical operation using themicroscope, for example, to observe a small region around a lesion inorder to work on it, may find it difficult to perform the desiredoperations properly.

Condition (2) defines the minimum object-side numerical aperture of theoptical system of the imaging unit of the three-dimensional imageobservation microscope system. When Condition (2) is not satisfied, theimage obtained has an insufficient three-dimensional appearance.Therefore, for example, when an operator works on a lesion whileobserving the image, it is difficult for him to identify the positionalrelationship between the operation tool such as a surgical knife and thelesion.

Condition (3) defines the positional relationship between adjacent imagepickup surfaces of image pickup devices on the optical axis of theoptical system of the imaging unit. When the lower limit of Condition(3) is not satisfied, two images obtained by the image pickup devicesare not sufficiently different in contrast. Consequently, when twoimages that are focused on different points and displayed by the displayunit as overlaid images in the line of sight, the viewer does notperceive a three-dimensional appearance based on the difference incontrast between two images and does not recognize the displayed imagesas a three-dimensional image. When the upper limit of Condition (3) isnot satisfied, the difference in contrast between two images obtained bythe image pickup devices becomes excessively large and two imagesdisplayed on the display unit do not have a close enough relationship.Consequently, the viewer does not recognize the displayed images as athree-dimensional image.

The display unit of the three-dimensional image observation microscopesystem overlays images that are focused at different object distancesand captured by the imaging unit in the line of sight of the viewer asfollows. An image focused on an object point that is closer to theimaging unit is displayed at a position that is closer to the viewer,and an image focused on an object point that is farther away from theimaging unit is displayed at a position that is farther away from theviewer.

It is desirable that a display surface 1 and a display surface 2 thatare in the line of sight of the observer but at different distances fromthe observer satisfy the following conditions:αn>a·E/(D+a)  Condition (4)αf>a·E/D  Condition (5)where

-   -   αn is the size that an object point image that is displayed on a        display surface 2 that is farther away from the viewer has when        it is displayed on a display surface 1 that is closer to the        viewer;    -   a is the distance, between the display surface 1 and the display        surface 2;    -   E is the interpupillary distance of the viewer;    -   D is the distance between the viewer's observation position and        the display surface 1 that is closer to the viewer; and    -   αf is the size that an object point image that is displayed on        the display surface 1 that is closer to the viewer has when it        is displayed on the display surface 2 that is farther away from        the viewer.

A display unit must satisfy Conditions (4) and (5) above in order forthe viewer to recognize images overlaid in his line of sight as athree-dimensional image. Images of one and the same object point thatare displayed on the display surfaces 1 and 2 should be seen asoverlapped when the viewer views them with both eyes. To this end, it isdesirable that both Conditions (4) and (5) above be satisfied. When thedisplay unit fails to satisfy at least one of Conditions (4) and (5), itis difficult for the viewer to observe the displayed image inthree-dimensions, which causes undesirable eye fatigue.

The viewer generally has an interpupillary distance of approximately 55to 75 mm. Therefore, E in Conditions (4) and (5) is first set for 80 mmor larger, and then the other parameters are determined. In this manner,a display unit providing three-dimensional observation for most viewerscan be made available. By using E of a higher value, a motion parallaxeffect is added to the displayed image. In this way, the viewer canobserve a natural three-dimensional image without failing to perceive athree-dimensional appearance even if he moves his line of sight withinthe display surface of the display unit.

In order to satisfy Conditions (4) and (5), it is desirable that thedisplay unit has a digital zoom function in order to control the displaymagnification of each display surface.

Additionally, in order for the viewer not to fail to perceive athree-dimensional appearance of the displayed image when he changes hisobservation position in relation to the display unit, it is desirablethat the imaging unit and the display unit satisfy the followingConditions (6) and (7):NAmax≧0.15  Condition (6)|βid·(Ii·tanγ)/D|≦10.2  Condition (7)where

-   -   NAmax is the maximum object-side numerical aperture of the        objective optical system of the imaging unit;    -   βid is the magnification at which an image that is formed on the        image pickup surface of the imaging unit is displayed on the        display surface closest to the viewer;    -   Ii is the distance, in mm, between the optical axis and a point        at the maximum image height on the image pickup surface of an        image pickup device provided in the imaging unit;    -   γ is the inclination relative to the optical axis of the        principal ray entering the image pickup surface of the image        pickup device provided in the imaging unit at the point of        maximum image height; and    -   D is the distance, in mm, between the viewer's observation        position and the display surface that is closest to the viewer.

Although the quantity D of Condition (7) above is defined more broadly(in relation to their possibly being more than two display surfaces)than the quantity D of Conditions (4) and (5) above is defined, bothdefinitions define the same feature when only two display surfaces arebeing considered.

When the maximum object side numerical aperture of the optical system ofthe imaging unit does not satisfy the lower limit of Condition (6)above, the image does not exhibit a sufficient three-dimensionalappearance when a microscopic object is observed at a highermagnification. Therefore, unfavorably, the viewer fails to perceive athree-dimensional appearance of the displayed image when he changes hisobservation position.

Condition (7) above optimizes the range in which the display unit candisplay three-dimensional images over the range of the image field ofthe imaging unit. When Condition (7) above is not satisfied, the rangein which the display unit can display three-dimensional images over theimage field of the imaging unit is reduced. Therefore, unfavorably, theviewer has a more limited range in which he can always recognizethree-dimensional images even if he changes his observation position.

Actual microscope observations often involve three-dimensional objectsurfaces that are tilted in relation to the optical axis of the opticalsystem of the imaging unit. In such cases, an unfocused image on theimage pickup surface can be corrected by tilting the image pickupsurface the same amount as the object surface about the optical axis ofthe image pickup surface of the image pickup device. Thus, it isdesirable that the optical system of the imaging unit be telecentric onthe image side.

Similarly in the display unit, the display surface is tilted the sameamount as the image pickup surface about the center of the displaysurface and the image display magnification is controlled for eachdisplay surface according to the inclination of the image pickupsurface. In this manner, a natural three-dimensional image with nodistortion from the center to the periphery can be reproduced. Toaccomplish this, it is desirable that the display unit includes amechanism that detects the inclination of the image pickup surface inrelation to the optical axis and that determines the displaymagnification at each display surface, as well as a mechanism to processthe images based on the determined display magnification.

Using the structure described above, a three-dimensional imageobservation microscope system is provided wherein an observed object isdisplayed as a three-dimensional image that includes sufficientthree-dimensional information for surgical operations under themicroscope, that favorably reproduces the three-dimensional appearanceof an observed object in the line of sight of the viewer, and that doesnot cause eye fatigue of the viewer even after prolonged periods ofobservation.

Embodiments 1-5 of the present invention will now be individuallydescribed with reference to the drawings.

EMBODIMENT 1

FIGS. 1 and 2 show the imaging unit and display unit, respectively, ofthe three-dimensional image observation microscope system of Embodiment1.

Referring to FIG. 1, the imaging unit has an optical system thatsatisfies Conditions (1), (2), and (3) above and includes, arranged inorder from the object side, an objective lens 1 that collimates thelight from an object O, a zoom optical system 2 that afocally zooms alight beam from the objective lens 1, an imaging lens 3 that forms animage carried by the afocal light beam emerging from the zoom opticalsystem 2, a beam splitter 4 that splits the light beam from the imaginglens 3, and image pickup surfaces In and If of imaging devices 5 and 6that capture images carried by the light beams split by the beamsplitter 4.

FIG. 1 shows the positional relationship between the image position I ofan object O and the conjugate positions In′ and If′ of the image pickupsurfaces In and If. Assuming that the distances between In and If andbetween In′ and If are d, the image pickup surfaces are preferablypositioned so that the distance between the image position I and In orIf is d/2. With this structure, images focused at different object pointdistances in the optical axis direction on either side of the object Ocan be captured at a desired magnification.

As shown in FIG. 2, the display unit includes a display 7 that displaysan image captured by the image pickup surface In and a display 8 thatdisplays an image captured by the image pickup surface If at a distancea from each other. A viewer 9 observes the display surface at a distanceD from the nearest display.

The image display magnification is controlled so that the image size αfthat an object point image f displayed on the display 7 has when it isdisplayed on the display 8 and the image size an that an object pointimage e displayed on the display 8 has when it is displayed on thedisplay 7 satisfy Conditions (4) and (5) above when the viewer 9observes the display surfaces with both eyes.

It is desirable that the difference in contrast between the imagesdisplayed on the two displays be nearly equal to the difference in MTF(modulation transfer function) between the image pickup surfaces In andIf. For this purpose, the display unit has a mechanism to performspecific calculations based on image signals obtained by the imagepickup devices (not shown) and an image processing mechanism such as adigital zoom (not shown). In this way, contrast images are displayed inthe line of sight of the viewer 9, by which the viewer 9 can observe anenlarged three-dimensional image having a natural appearance, similar toa directly viewed image of an object.

It is also desirable that the imaging unit and display unit satisfyCondition (7) above so that images obtained by the imaging unit requireless processing by the display unit.

In addition, it is desirable that the displays of the display unit be,for example, transmission type liquid crystal displays. Further, animage synthesis optical system such as a half mirror may be provided onthe optical path of the display unit.

EMBODIMENT 2

FIGS. 3 and 4 show the imaging unit and display unit, respectively, ofthe three-dimensional image observation microscope system of Embodiment2.

The imaging unit includes an optical system satisfying Conditions (1)and (2) above and includes, arranged in order from the object side wherethe reference symbol O for object is located in FIG. 3, an afocalobjective lens 1, an afocal zoom optical system 2 that afocally zooms anafocal light beam from the objective lens 1, an imaging lens 3 thatforms an image carried by the afocal light beam emerging from the afocalzoom optical system 2, a trisecting prism 10 that splits the light beamfrom the imaging lens 3, and three image pickup devices 11, 12, and 13that capture images carried by the light beams split by the trisectingprism.

FIG. 3 shows the positional relationship between the image position I ofan object O and the image pickup surface 14 of the image pickup device11, the conjugate position 15 of the image pickup surface of the imagepickup device 12, and the conjugate position 16 of the image pickupsurface of the image pickup device 13. The imaging device of thisembodiment has three image pickup surfaces (in this case, planarsurfaces) arranged on either side of the image position I of the objectO, and the following Conditions (3-1) and (3-2) are satisfied:0.25≦d1·NA/(R·β)≦2  Condition (3-1)0.25≦d2·NA/(R·β)≦2  Condition (3-2)where

-   -   d1 is the distance between the image pickup surface 14 of the        image pickup device 11 and the conjugate position 15 of the        image pickup surface of the image pickup device 12;    -   d2 is the distance between the conjugate position 15 of the        image pickup surface 12 and the conjugate position 16 of the        image pickup surface of the image pickup device 13; and    -   NA, R and β are as defined for Conditions (1)-(3) above.

As shown in FIG. 4, the display unit includes a display 17 that isnearest the observer that displays an image captured by the image pickupsurface 14, a display 18 (that, of three displays 17, 18 and 19 is amid-distance from the observer) that displays an image captured by theimage pickup surface of the image pickup device 12, and a display 19that is farthest from the observer and that displays an image capturedby the image pickup surface of the of the image pickup device 13.

The image display magnification is controlled so that Conditions (4-1)and (5-1) below are satisfied. Furthermore, the image displaymagnification is controlled so that Conditions (4-2) and (5-2) below aresatisfied:αn1>a1·E/(D1+a1)  Condition (4-1)αf1>a1·E/D1  Condition (5-1)αn2>a2·E/(D2+a2)  Condition (4-2)αf2>a2·E/D2  Condition (5-2)where

-   -   αn1 is the image size that an object point image pf1 that is        displayed on the display 18 has when it is displayed on the        display 17;    -   a1 is the distance between the display 17 and the display 18;    -   E is the interpupillary distance of the viewer (desirably, E=80        mm or larger);    -   D1 is the distance between a viewer 20 and the display 17;    -   αf1 is the image size that an object point image pn1 that is        displayed on the display 17 has when it is displayed on the        display 18;    -   αn2 is the size that an object point image pf2 that is displayed        on the display surface 19 has when it is displayed on the        display surface 18;    -   a2 is the distance between the displays 18 and 19;    -   αf2 is the size that an object point image pn2 that is displayed        on the display surface 18 has when it is displayed on the        display surface 19; and    -   D2 is the distance between the viewer 20 and the display 18.

It is desirable that the differences in contrast among images displayedon the three displays be nearly equal to the differences in MTF amongthe respective image pickup surfaces. For this purpose, the display unithas a mechanism to perform specific calculations based on image signalsobtained by the image pickup devices (not shown) and an image processingmechanism such as a digital zoom (not shown). In this way, contrastinformation contained in images displayed in the line of sight of theviewer 20 is increased in density, by which the viewer 20 can observe anenlarged three-dimensional image having a more natural appearance.

The image pickup devices of the imaging unit and the displays of thedisplay unit can be increased in number. In such cases, it is desirablethat three image pickup surfaces that are near to each other on theoptical axis of the optical system of the imaging unit satisfyConditions (3-1) and (3-2) above and the display surfaces of threedisplays that are near to each other in the line of sight of the viewer20, on which the images obtained by the three image pickup surfaces aredisplayed, satisfy Conditions (4-1) and (5-1) above, as well asConditions (4-2) and (5-2) above.

In the imaging unit of Embodiments 1 and 2 above, the light beam issplit on the image side of the imaging lens 3. However, the light beamcan be split on the object side of the imaging lens 3.

EMBODIMENT 3

FIGS. 5 and 6 show the imaging unit and the display unit, respectively,of the three-dimensional image observation microscope system ofEmbodiment 3. This embodiment has the same basic system structure asEmbodiment 1. Therefore, only an explanation of aspects of the structurethat differ from Embodiment 1 will be given below.

Actual microscopic observation in Embodiment 3 involvesthree-dimensional object surfaces that are tilted relative to theoptical axis of the optical system of the imaging unit. Therefore, theimage pickup surfaces of the imaging unit of this embodiment are tiltedaccording to the inclination of the object surface. Furthermore, theinclinations of the image pickup surfaces are controlled in associationwith a zoom lens mechanism or a focusing mechanism that is provided inthe optical system of the imaging unit so that images are always focusedon the object surface.

On the other hand, the display unit detects the inclinations of theimage pickup surfaces and tilts the display surfaces of the displays thesame amount as the image pickup surfaces are tilted. In this way, theinclination of an observed surface in relation to the optical axis ofthe optical system of the imaging device is taken into account. Thus, aviewer 9 can observe an image displayed on the display unit as a naturalthree-dimensional image without distortion from the center to theperiphery of the field of view. As shown in FIGS. 5 and 6, theinclination of various surfaces are indicated as an angle θ.

EMBODIMENT 4

FIGS. 7 and 9 show the imaging unit and display unit, respectively, ofthe three-dimensional image observation microscope system of Embodiment4.

As shown in FIG. 7, the imaging unit includes, in order from the objectside: an objective lens 21 that obtains an image of an object and emitsa collimated light beam; a zoom optical system 22 that afocally zoomsthe light beam from the objective lens 21; relay lenses 23L, 23R thatrelay the pupil of the zoom optical system; a beam splitter 24 that isprovided in the relay lenses for splitting the light into an opticalpath for obtaining a left eye image and an optical path for obtaining aright eye image; aperture diaphragms 28L and 28R that are provided inthe optical paths split by the beam splitter at eccentric positions inrelation to the optical axis, for adding parallax information to imagesobtained by left and right image pickup devices; imaging lenses 29L and29R that form images carried by the light beams that have passed throughthe aperture diaphragms on the image pickup surfaces of image pickupdevices; beam splitters 30L and 30R that split the imaging light beamsfrom the imaging lenses into two optical paths; and image pickupsurfaces 32L, 33L and 32R, 33R provided on either side of the imagepositions 31L and 31R of an object O for capturing object images focusedon different positions. The beam splitter 24 and the reflecting members25, 26 and 27 that control the distance between the left and rightoptical paths are provided within the optical paths of the left andright relay lenses 23L, 23L, 23R and 23R.

FIG. 7 shows the positional relationship among the image positions 31L,31R of the object O, the image pickup surfaces 32L, 32R and theirconjugate positions 32L′, 32R′, and the image pickup surfaces 33L, 33Rand their conjugate positions 33L′, 33R′. In the imaging unit of thisembodiment, the image pickup surfaces are provided on either side of theimage position of the object O, and the following Condition (8) issatisfied:0.25≦dNAlr/(R·β)≦2  Condition (8)where

-   -   d is the distance, in mm, between the image pickup surfaces and        the conjugate positions of the image pickup surfaces of the        image pickup devices;    -   NAlr is the object-side numerical aperture of the objective lens        of the imaging unit when the zoom optical system has a        magnification β;    -   R is the width, in mm, of a pair of black and white lines when        the pair of black and white lines are part of a test chart        having evenly-spaced, parallel sets of black and white lines and        the test chart is placed in a plane that is conjugate with an        image pickup surface of one of the image pickup devices with        respect to the objective lens of the imaging unit so that an        image of the pair of black and white lines is captured on the        image pickup surface of one of the image pickup devices in such        a manner that the black and white lines are displayed on a        monitor with a contrast of 10% through a circuit system that        processes image signals sent from the image pickup devices; and    -   β is the magnification of the zoom optical system.

Additionally, it is desirable that the imaging unit of Embodiment 4 ofthe present invention satisfies the following Conditions (9) and (10):fob·NAlrmax≧15 mm  Condition (9)NAlrmin≧0.02   Condition (10)where

-   -   fob is the focal length, in mm, of the objective lens of the        imaging unit;    -   NAlrmax is the maximum object-side numerical aperture of the        objective lens of the imaging unit; and    -   NAlrmin is the minimum object-side numerical aperture of the        objective lens of the imaging unit.

With the imaging unit having the above structure, information ofparallax and contrast in the line of sight can be provided asinformation for the viewer in order for the viewer to perceive athree-dimensional image.

FIG. 8 shows the apertures 35L and 35R of left and right aperturediaphragms 28L and 28R, respectively, being projected onto andoverlapped with the aperture 34 of the zoom optical system, whichdefines the aperture of the imaging unit in order to show how large theaperture diameter of the imaging unit can be when the left and rightaperture diaphragms are provided at eccentric positions in relation tothe optical axis. As shown in FIG. 8, the left and right aperturediaphragms of Embodiment 4 have an aperture diameter larger than halfthe aperture diameter of the imaging unit with no left and rightaperture diaphragms. This ensures sufficient parallax while the opticalsystem has a large aperture.

As shown in FIG. 9, the display unit of Embodiment 4, includes, arrangedin order from the farthest position from the observation position of theviewer 41, displays 36L and 36R that display images obtained by the leftand right image pickup surfaces 33L and 33R, displays 37L and 37R thatdisplay images obtained by the left and right image pickup surfaces 32Land 32R, and left and right ocular lenses 38L and 38R that enlargeimages displayed on the displays for observation. Reflecting members39L, 39R and 40L, 40R that control the distance between the left andright optical paths according to the interpupillary distance of theviewer are provided in the optical path of the ocular lens. In FIG. 9,Ee, Ee designate regions for obtaining three-dimensional observation.The observer can view three-dimensional images when he puts his left andright eyes in the regions Ee, Ee, respectively.

It is also desirable that the display unit of Embodiment 4 of thepresent invention satisfy the following Conditions (11) and (12) so thatimages on the displays 37L and 37R and images on the displays 36L and36R are overlapped regardless of which eye the viewer moves within therange Ee:αne>ae·Ee/(2·foc+ae)  Condition (11)αfe>ae·Ee/2·foc  Condition (12)where

-   -   αne is the image size that an object point image fe displayed on        the display surface of the display 36L has when it is displayed        on the display surface of the display 37L;    -   ae is the distance between the display surfaces of the displays        36L and 37L;    -   Ee is the range of adjustment of the interpupillary distance of        the ocular lens of the display unit for three-dimensional        viewing;    -   foc is the focal length of the ocular lens; and    -   αfe is the image size that an object point image fg displayed on        the display surface of the display 37L has when it is displayed        on the display surface of the display 36L.

FIG. 10 shows the relationships of parameters of the left eye displayunit. The right eye display unit has the same relationships, andtherefore, a separate explanation of its arrangement will not beprovided.

As described above, contrast information is added to images displayed inthe line of sight of the viewer 41 and parallax information is furtheradded to divided right and left eye images, thereby ensuringreproduction of a three-dimensional appearance that is in no wayinferior to direct visual observation of an object providingthree-dimensional images. The three-dimensional image observationmicroscope system of Embodiment 4 of the present invention providesenlarged images for three-dimensional image observation that allows theobserver to perceive a natural appearance and does not cause eye fatigueafter prolonged observation.

Most people have an interpupillary distance of 55 to 75 mm and a maximumpupil diameter of approximately 7 mm. With the right and left ranges ofEe being apart from each other 65 mm and having a diameter of 13.5 mm,most people can receive the benefit of three-dimensional observationwithout adjusting the interpupillary distance. With the range Ee havinga larger diameter, motion parallax effect is added and an enhancedthree-dimensional appearance can be obtained. For example, an excellentthree-dimensional appearance is preferably obtained when Ee has adiameter of approximately 20 mm.

It is desirable that the displays of the display unit be, for example,transmission-type liquid crystal displays. An image synthesis opticalsystem such as a half mirror can be provided in the optical path of thedisplay unit.

EMBODIMENT 5

FIG. 11 shows the configuration of the three-dimensional imageobservation microscope system of Embodiment 5. The three-dimensionalimage observation microscope system of this embodiment is formed of animaging apparatus (shown in the top portion of FIG. 11) and a displayapparatus. The display apparatus is formed of an image processor (shownin the middle portion of FIG. 11) and an image display (shown in thebottom portion of FIG. 11). The imaging apparatus has the same structureas that of Embodiment 2 from the objective lens 1 to the imaging lens 3,and thus further description thereof will be omitted. A micro-lens array50 is provided between the imaging lens 3 and an image pickup surface 52of an image pickup device 53. The image pickup surface 52 of the imagepickup device 53 is provided on the object side of a point 51 where animage of an object O is formed by the optical system (which includes theobjective lens 1 to the micro-lens array 50).

An image that is captured by the image pickup device 53 is displayed onone or more displays M(i), where i may equal 1 to n and n is a naturalnumber of 2 or higher, that is provided in the image processor. Thedisplays M(i) are each provided with a micro-lens array 54. The displaysurface of each of the displays M(i) is positioned at the focal point 55of a micro-lens array 54.

FIG. 12 is an enlarged view of the image pickup surface 52 of the imagepickup device 53 and its surrounding area in the imaging apparatus. FIG.13 is an enlarged view of the display surface of the display M(i) andits surrounding area in the image processor. In this embodiment, thefollowing Condition (13) is satisfied:bb/BB=dd/DD=ee/EE  Condition (13)where

-   -   bb is the distance between pixels of the image pickup device 53;    -   BB is the distance between picture elements of the display M(i),        where i may equal 1 to n and n is a natural number of 2 or        higher;    -   dd is the distance between adjacent micro-lenses of a micro-lens        array 50 that is provided between the imaging lens and an image        pickup surface 52 of the image pickup device 53;    -   DD is the distance between adjacent micro-lenses of a micro-lens        array 54 that is associated with the display M(i), where i        equals 1 to n and n is a natural number of 2 or higher;    -   ee is the distance between the micro-lens array 50 and the image        pickup surface 52 of the image pickup device 53; and    -   EE is the distance between the display surface of the display        M(i) and the micro-lens array 54 (see FIG. 13), where i equals 1        to n and n is a natural number of 2 or higher.

In this way, an image captured through the micro-lens array 50 isdisplayed on the display surface of the display M(i) and observedthrough the micro-lens arrays 54, the image being observed as athree-dimensional image. An image captured by the image pickup device 53is shared by the display surfaces of the displays M(i). Therefore,overlaid images observed through the micro-lens arrays 54 are all thesame size.

The image processor (middle portion of FIG. 11) comprises imaging lensesL1 to Ln and image pickup devices I1 to In for capturingthree-dimensional images through the micro-lens arrays 54. The imagepickup devices I1 to In capture images focused on different points O1 toOn through the imaging lenses L1 to Ln.

Images captured by the image pickup devices I1 to In are displayed ondisplays P1 to Pn provided in the image display (bottom portion of FIG.11). The displays P1 to Pn are provided at intervals within the line ofsight of a viewer 56. The displays Pi−1 and Pi+1 placed immediatelybefore and after a display Pi (where i is any natural number of 2 orhigher) satisfy the above Conditions (4-1), (4-2), (5-1), and (5-2).

An image focused on the point 01 closest to the image pickup device inthe image processor is displayed on the display P1 closest to the viewer56 in the image display. An image focused on a point O2 that is closerto the display surface of the display than the focused point O1 in theimage processor is displayed on the display P2 that is farther away fromthe viewer 56 than the display P1 in the image display.

With this structure, the viewer 56 can observe an object image capturedby the imaging apparatus through the display apparatus as athree-dimensional image. With just one image pickup device, the imagingapparatus of this embodiment can be reduced in size and weight. With theimage processor provided in the display apparatus, the three-dimensionalimage observed by the viewer 56 through the image display can be easilyadjusted for better three-dimensional appearance. The image processor ofthe display apparatus can be placed somewhere not disturbing the viewer56 at work. Only the imaging apparatus and the image display of thedisplay apparatus are placed close to the viewer 56, thereby creating anenvironment in which the viewer 56 can easily conduct his work.

Additionally, the image processor can be replaced with arithmeticcircuits for image analysis. In such a case, the arithmetic circuitscreate multiple images focused on different points based on imagescaptured by the imaging apparatus and display them on the image display,by which a similar three-dimensional image can be observed.

FIG. 14 shows a pair 74, 78 of black and white lines that form part of atest chart, and FIG. 15 shows a test chart TC that includes the pair ofblack and white lines shown in FIG. 14 positioned at a location in frontof the objective lens 1 of Embodiment 1 at a position that is conjugatewith an image pickup surface of one of the image pickup devices.

The present invention is not limited to the aforementioned embodiments,as it will be immediately apparent that various alternativeimplementations are possible. Such variations are not to be regarded asa departure from the spirit and scope of the present invention. Rather,the scope of the present invention shall be defined as set forth in thefollowing claims and their legal equivalents. All such modifications aswould be obvious to one skilled in the art are intended to be includedwithin the scope of the following claims.

1. A three-dimensional image observation microscope system comprising:an imaging unit that captures images focused at different object pointdistances in an optical axis direction; and a display unit that displaysa plurality of images that are captured by the imaging unit for overlaidobservation along the line of sight of a viewer; wherein the imagingunit includes an objective optical system that obtains an image of anobject, a zoom optical system that controls the magnification of theimage obtained by the objective optical system, and a plurality of imagepickup devices that capture images having a magnification that iscontrolled by the zoom optical system; and the following conditions aresatisfied:fob·NAmax≧15 mmNAmin≧0.020.25≦d·NA/(R·β)≦2  where fob is the focal length, in mm, of theobjective optical system; NAmax is the maximum object-side numericalaperture of the objective optical system of the imaging unit; NAmin isthe minimum object-side numerical aperture of the objective opticalsystem of the imaging unit; d is the distance, in mm, between twoadjacent image pickup surfaces of the image pickup devices; NA is theobject-side numerical aperture of the objective optical system of theimaging unit when the zoom optical system has a magnification β; R isthe width, in mm, of a pair of black and white lines when the pair ofblack and white lines are part of a test chart having evenly-spaced,parallel sets of black and white lines and the test chart is placed in aplane that is conjugate with an image pickup surface of one of the imagepickup devices with respect to the objective optical system of theimaging unit so that an image of the pair of black and white lines iscaptured on the image pickup surface of one of the image pickup devicesin such a manner that the black and white lines are displayed on amonitor with a contrast of 10% through a circuit system that processesimage signals sent from the image pickup devices; and β is themagnification of the zoom optical system.
 2. The three-dimensional imageobservation microscope system of claim 1, wherein: the display unitincludes a plurality of display surfaces in the line of sight of theviewer; an image focused on an object closer to the imaging unit isdisplayed at a position closer to the viewer, and an image focused on anobject farther away from the imaging unit is displayed at a positionfarther away from the viewer; said plurality of display surfaces are twodisplay surfaces that are adjacent to one another in the line of sightof the viewer; and the following conditions are satisfied:αn>a·E/(D+a)αf>a·E/D where αn is the size that an object point image that isdisplayed on one of said two display surfaces, namely, the displaysurface that is farther away from the viewer, has when it is displayedon the other of said two display surfaces that is closer to the viewer;a is the distance between said two display surfaces; E is theinterpupillary distance of the viewer; D is the distance between theviewer's observation position and the display surface that is closer tothe viewer; and αf is the size that an object point image displayed onthe display surface that is closer to the viewer has when it isdisplayed on the display surface that is farther from the viewer.
 3. Thethee-dimensional image observation microscope system of claim 2,wherein: the imaging unit and the display unit satisfy the followingconditions:NAmax≧0.15|βid·(Ii·tan γ)/D|≦1 0.2 where βid is the magnification at which animage formed on the image pickup surface of the image pickup device isdisplayed on the display surface that is closer to the viewer, Ii is thedistance, in mm, between an optical axis and a point at the maximumimage height on the image pickup surface of an image pickup deviceprovided in the imaging unit; and γ is the inclination, in relation tothe optical axis, of the principal ray entering the image pickup surfaceof the image pickup device provided in the imaging unit at said point ofmaximum image height.
 4. A thee-dimensional image observation microscopesystem comprising: an imaging unit that captures images focused atdifferent object point distances in an optical axis direction; and adisplay unit that displays a plurality of images captured by the imagingunit for overlaid observation along the optical axis of an ocular lens;wherein the imaging unit includes, in order from an object side, anobjective lens that obtains an object image and emits a collimated lightbeam, a zoom optical system that afocally zooms the light beam from theobjective lens, a relay lens that relays a pupil in the zoom opticalsystem, a beam splitter provided in the relay lens to split light intoan optical path for obtaining a left eye image and an optical path forobtaining a right eye image, aperture diaphragms in the optical pathssplit by the beam splitter at eccentric positions in relation to theoptical axis of the relay lens for adding parallax information toimages, imaging lenses that form images carried by the light beams thathave passed through the aperture diaphragms, and image pickup deviceslocated before and after the object image position so as to captureobject images focused on different positions; and the followingcondition is satisfied:0.25≦d·NAlr/(R·β)≦2 where d is the distance, in mm, between two adjacentimage pickup surfaces of the image pickup devices; NAlr is theobject-side numerical aperture of the objective lens of the imaging unitwhen the zoom optical system has a magnification β; R is the width, inmm, of a pair of black and white lines when the pair of black and whitelines are part of a test chart having evenly-spaced, parallel sets ofblack and white lines and the test chart is placed in a plane that isconjugate with an image pickup surface of one of the image pickupdevices with respect to the objective lens of the imaging unit so thatan image of the pair of black and white lines is captured on the imagepickup surface of one of the image pickup devices in such a maimer thatthe black and white lines are displayed on a monitor with a contrast of10% through a circuit system that processes image signals sent from theimage pickup devices; and β is the magnification of said zoom opticalsystem.
 5. The three-dimensional image observation microscope system ofclaim 4, wherein: the display unit includes a plurality of displaysdisplaying both left and right images obtained by the image pickupdevices of the imaging unit, and a pair of ocular lenses for enlargingfor observation the images displayed on the plurality of displays; theplurality of displays are provided on the optical axis of each of theocular lenses so that an image of an object point that is closer to theimaging unit is displayed at a position closer to the ocular lens and animage of an object point that is farther away from the imaging unit isdisplayed at a position farther away from the ocular lens; and thedisplay surfaces of adjacent displays on the optical axes of the ocularlenses satisfy the following conditions:αne>ae·Ee/(2·foc+ae)αfe>ae·Ee/(2·foc) where αne is the size that an object point imagedisplayed on a display surface of a display that is farther away from anocular lens has when it is displayed on a display surface of a displaythat is closer to the ocular lens; ae is the distance between thedisplay surfaces of the displays; Ee is the range of adjustment of theinterpupillary distance of the ocular lenses of the display unit; foc isthe focal length of an ocular lens; and αfe is the size that an objectpoint image displayed on the display surface of the display that iscloser to an ocular lens has when it is displayed on the display surfaceof the display that is farther away from the ocular lens.
 6. Thethree-dimensional image observation microscope system of claim 4,wherein the imaging unit further satisfies the following conditions:fob·NAlrmax≧15 mmNAlrmin≧0.02 where fob is the focal length, in mm, of the objective lensof the imaging unit; NAlrmax is the maximum object-side numericalaperture of the objective lens of the imaging unit; and NAlrmin is theminimum object-side numerical aperture of the objective lens of theimaging unit.